1. Technical Field of the Invention
This invention relates to mobile services in telecommunication networks and, more particularly, to a method of performing enhanced mobility management for mobile stations in Simple IP telecommunication networks when performing Layer 2 Tunneling Protocol (L2TP) tunneling.
2. Description of Related Art
Modern telecommunication networks allow mobile subscribers to benefit from a vast array of services. In the field of wireless communications for instance, mobile stations support a wide variety of applications through which mobile subscribers, in addition to having conversations, can send text or vocal messages to other subscribers, and surf on the Internet.
The essence of mobile services hence lies in the opportunity for mobile subscribers to benefit at all times from the aforementioned services, regardless of location within the coverage area of the telecommunication network. To guarantee adequate service provision, telecommunication network operators must consequently ensure that their equipment is configured efficiently, such that connections established between the mobile stations and service nodes in the telecommunication network are appropriately monitored and maintained.
Several methods have been developed to manage the procedures following which the service nodes in a telecommunication network cooperate in handling the connections established between said service nodes in the telecommunication network and mobile stations. These procedures, or algorithms regulating the functionality of the service nodes, hold great importance as they are intimately linked to the quality of services provided to subscribers.
Mobile subscribers indeed expect to be able to communicate amongst themselves, and benefit from data transfer services which have been subscribed to, without any significant disturbance or malfunction affecting the quality of said services: a sudden interruption or termination of an ongoing communication session due to loss of information in the telecommunication network, or excessive signal attenuation rendering use of the mobile station inadequate within the coverage area of the telecommunication network.
Protocols have thus been defined in a quest to develop the most efficient procedures possible to manage exchanges of information between mobile stations and telecommunication networks. Mobile IP is one of those protocols aiming at providing mobile stations with efficient service provision.
Mobile IP is a protocol relating to the management of mobile station addresses in telecommunication networks, whereby two IP addresses are associated with a mobile station: a fixed IP address (home address) and a “care-of” IP address that changes at each new “point of attachment”. The fixed IP address is assigned to the mobile station upon registering in the telecommunication network it subscribes to (home telecommunication network). Upon the establishment of a connection with a foreign telecommunication network, the mobile station registers as well with a Home Agent (HA) node in the telecommunication network. The HA stores the mobile station's fixed IP address and associates the latter with an IP “point-of-attachment address”, which is an indicator of the IP address of the telecommunication network within which the mobile station is currently located. The HA manages this IP “point-of-attachment” address.
Every time the mobile station transits from the coverage area of a first telecommunication network to that of a second telecommunication network, the mobile station performs a new registration with the foreign telecommunication network and as well with the HA. During this new registration, the HA updates the mobile station's IP “point-of attachment” address, such as to reflect the address of the foreign telecommunication network.
The HA then collects in the mobile station's home telecommunication network the packets intended for the mobile station from the delivery point associated with the mobile station's fixed IP address and home IP “point-of-attachment” address; the HA forwards these packets to the appropriate delivery point associated with the mobile station's fixed IP address and new “point-of-attachment address” in the foreign telecommunication network, thereby ensuring proper delivery.
In this fashion, upon registering in the foreign telecommunication network, the mobile station is not assigned a new local IP address but rather retains ownership of its fixed IP address. The mobile station may at all times be reached with this fixed IP address since the HA takes care to update the mobile station's “point-of-attachment address” and to forward information intended for the mobile station from the mobile station's home telecommunication network to the visited telecommunication network.
Simple IP is another protocol aiming at an efficient management of mobile subscriber mobility and effective service provision in a telecommunication network. Simple IP enables the establishment of a tunneled connection between a service node and an endpoint, or terminal node, in the telecommunication network, such that they may exchange information. This can be performed to establish an end-to-end connection from the mobile station to the terminal node. Once the tunnel is established between the service node and the terminal node, the service node from thereon acts as a transparent router, simply forwarding information exchanged between the mobile station and the terminal node.
The benefits of tunneling reside in that they for one allow the establishment of virtual private networks (VPNs) between two points in the telecommunication network, and also allow the processing of packets to be independent from the nature of the tunnel endpoints.
Despite the aforementioned tunneling advantages, the current Simple IP protocol nonetheless presents inadequacies, as undesired events affecting the quality of service provision to mobile stations can possibly occur. Indeed, depending on how service nodes in telecommunication networks relay each other in handling the connections established with the mobile stations as the latter transit from the coverage area of a service node to that of another, the quality of service provision may find itself degraded, as a result of which communication, or data transfer services, may be lost.
In accordance with the current Simple IP protocol, an address is assigned to the mobile station upon the establishment of a connection between the mobile station and the terminal node via a first service node. However, if the mobile station transits from the coverage area of the first service node to that of a second service node in the telecommunication network, the information sent by the terminal node to the mobile station via the first service node is lost, as the mobile station is no longer connected to said first service node. In other words, the use of an erroneous point of attachment is made, such that loss of data ensues in such a scenario.
Moreover, the connection established between the mobile station and the terminal node via the first service node is not immediately removed at once following the transiting of the mobile station from the coverage area of the first service node to that of the second service node, which results in inefficient bandwidth management. Indeed, this connection is only removed upon the expiry of a connection timeout, when no information has been sent over the connection for a pre-determined time interval.
In order to overcome the present flaws of the Simple IP protocol in the context of L2TP tunneling, it would be advantageous to have a method whereby subscribers could benefit from service provision of optimal quality without being subject to service failure, regardless of their location in the telecommunication network. It would be practical to have a procedure whereby service nodes and terminal nodes in the telecommunication network could cooperate in such a manner as to prevent undesired performance discrepancies, without having to equip current Simple IP telecommunication networks with costly additional nodes such as HAs for performing mobility management. The present invention provides such a system and method.